Browse Prior Art Database

Original Publication Date: 2001-Aug-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 30K

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The need for cheap computer memory continues to rise. In recent
years, the need for compact cheap flash memory is also increasing
due to the introduction of digital cameras smart cell phones and
compact operating systems such as Windows CE.

Current flash memory works by trapping charge in small conducting
volumes within the chip, or by injecting the charge into an
insulating film. Current dynamic memory stores charge on a

This disclosure describes new planar, memory cells based on
techniques similar to those used in electroplating of thin metallic
films. The advantages of this new approach over current
technologies are:

1) Fabrication is considerably simpler (batch) for similar size
charge storage device.
2) The final "L" and "0" states have similar potential energy so
there is no reason for the cell to "leak" making a good flash
3) For similar signal the volume of the cell can be smaller,
allowing the device to be further scaled to keep up with Moore's

Principle of Operation

Figure 1 shows the principle of operation of the simplest cell.
This cell consists of an electrolyte, two inert electrodes and a
small amount of material which can be moved between the electrode
by applying a voltage. Reversing the voltage reverses the direction
of transport. A "L" or "0" is represented by whether the material
is on one or other electrode. A gray scale could also be made by
using intermediate states in which some matrial is on each
electrode. Writing the cell is done by applying a pulse or sequence
of pulses to the cell to define the position of the deposit on the
electrodes. Reading the cell is done by applying a voltage in one
direction. If the deposit is on one electrode then it will begin to
transfer to the other by electrolysis and a current will flow. Once
the material has moved across the current will stop, assuming that
no other electrolytic process can happen. If the deposit is already
on the other electrode no current will flow. This current pulse is
used to read "L" and "0". The length of the current pulse could be
used as a gray scale memory. The reading process is thus
destructive and the cell must be rewritten after reading. A
macroscopic version of this cell has been demonstrated with gold


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electrodes, copper sulfate and sulfuric acid electrolyte and copper

Figure 2 experimental results from a cell.

Figure 2 shows a demonstration of such a cell. Initially the cell
is set to "L". Trace (a) shows the current when a voltage is
applied. The voltage starts at -2 V and is gradually increased
toward 0 V with time.The current flowing is limited to...